Integrated pest management: NSW case studies

Rabbits impact on

• threatened plant communities such as the Eastern Suburbs Banksia Scrub endangered ecological community at North Head
• cultural heritage sites like the Quarantine Station at North Head
• public open spaces such as national parks, picnic areas, council parks, sports fields, golf courses and footpaths, and suburban gardens

Several control methods are used to reduce the impacts from rabbits.

Chemical control: Monitoring rabbit numbers, scats and other signs helps agencies determine when population levels are high enough to require chemical control. Pindone baiting is used in national parks and also in urban areas where 1080 baiting is not permissible.

Biological controls: The myxomatosis virus, introduced to rabbit populations many decades ago, can help keep rabbit numbers low if they are prevalent during summer. The Office of Environment and Heritage (OEH) and other land management agencies can also release carrots contaminated with the Rabbit Haemorrhagic Disease Virus (RHDV or calicivirus) in late summer when conditions are most suited to its spread. Rabbits can develop immunity to RHDV, so populations are tested for their susceptibility to the virus before its release. Physical controls can be implemented immediately after a biological control has affected a rabbit population to take advantage of the population decline.

Physical controls: Ground shooting is undertaken in suitable open spaces to maintain a rabbit population at low numbers. It can be used to control small isolated populations or after poison baiting or biological controls have had an effect.

Rabbits in northern Sydney rarely construct underground warrens but they do take advantage of dense weedy undergrowth often found at the edge of grassy open space. Removing this undergrowth after rabbit numbers have been reduced by baiting or disease makes it difficult for remaining rabbits to flourish. If weed removal is undertaken when rabbit populations are booming, many rabbits will simply disperse and set up new populations in new areas.

Foxes are a pest which threaten native wildlife. OEH is conducting a fox control program in Kangaroo Valley to protect the endangered brush-tailed rock-wallaby. This program involves combining chemical and physical control methods. Fox abundance is monitored twice a year to help evaluate the program. Sand pads that record fox footprints give an indication of fox numbers.

Chemical control: Baiting is conducted at over 60 bait stations. Most stations are permanently covered by poison baits. The other stations (private properties where landholders do not want permanent baiting) are baited for one week each month. Different types of bait are used to try and attract as many foxes as possible.

Physical control: OEH also contracts two sessions of fox shooting or trapping in the area each year. This is to assist in controlling foxes that will not eat baits and foxes on properties where landholders are not interested in fox baiting.

Bitou bush is considered a major threat to biodiversity because

• it alters habitats by growing in dense thickets that smother native plants
• it provides a food source for other pest species

Throughout NSW, bitou bush is a threat to 157 plant species and 24 ecological communities.

Strategic control of bitou bush at Barrenjoey and Lion Island in north-east Sydney has resulted in a significant reduction of bitou bush and an improvement in the health, density and spread of Themeda grasslands. Schoolchildren can use Weeds Attack!, an online multimedia resource with interactive learning activities, to investigate the bitou bush weed.

Bitou bush is controlled using a combination of methods.

Chemical control: Aerial boom or spot spraying by helicopter is the best method for tackling bitou bush in otherwise inaccessible areas like coastal headlands, sea cliffs and islands. Spraying takes place in winter when native plants are semi-dormant and less susceptible to spray drift, and bitou bush is growing and highly susceptible to low doses of herbicide. Bitou bush flowers in winter and can easily be seen from the air and distinguished from native plants. Glyphosate or metsulfuron-methyl are the most commonly used herbicides. Aerial spot spraying is very accurate; a good operator can target a single bitou bush without harming the native vegetation around it. This National Parks and Wildlife Service video shows an aerial spraying program in Cape Byron Reserve.

Ground spot spraying or foliar (leaf) spraying is used where access is easier. Like aerial spraying, ground spot spraying takes place in winter. A low-pressure hand-held spray unit or a splatter gun is used. With the splatter gun, only a small amount of solution is needed on each plant.

The cut and paint method of applying herbicide is used in sensitive areas where spraying is not appropriate, for example adjacent to the fishermen’s cottages at Barrenjoey or in areas where bitou bush is invading littoral rainforest. This method, although time-consuming, poses no risk to surrounding native vegetation.

Physical control: Hand weeding is used as a follow-up control to remove bitou bush seedlings before they grow too big and dominate the surrounding vegetation.

Biological control: Bitou seed fly, bitou tip moth and the bitou leaf roller moth are all natural controls for bitou bush which have been trialled and released at Barrenjoey. There is evidence that some have spread to Lion Island. Tip moth and seed fly are now common in bitou bush areas.